Former Congresswoman Gabrielle Giffords took to social media to say: "My heart is with my former colleagues, their families & staff, and the US Capitol Police- public servants and heroes today and every day."

Giffords was shot in the head while meeting with constituents outside a store in Arizona in 2011. Six people were killed in that shooting.

My heart is with my former colleagues, their families & staff, and the US Capitol Police- public servants and heroes today and every day.